This invention relates to new and useful improvements in desalination system and comprises two embodiments.
In either case, considerable reduction of power requirements is obtained and a semi-automatic system results.
Vast areas of the earth are now relatively unpopulated, which would be quite habitable and very productive if adequate water could be supplied. The hot deserts and their semi-arid adjacent lands are conspicuous in this respect. The sea is often accessible to these lands with its virtually limitless supply of water, needing only to be desalinated.
In these areas money is often limited by the low density of population. Often skilled workmen are scarce, and always they must be assembled with great difficulty and at great expense.
In these places, it is crucial that structures be solid, durable, simple to maintain and to operate.
Many devices have been proposed to desalinate sea water and other contaminated water, cheaply. In general, these include elaborate heat exchange arrangements where contaminated water flows through a plurality of tubes or where contaminated water flows over or is cascaded over hot fresh water tubes.
Pluralities of tubes add a capital expense and they increase maintenance costs and operational cost. Further, the very slight scale formation on them greatly reduces the rate of heat transfer. While much heat is given off at the point of condensation, the transfer of that heat is very slow since water transmits heat some 400 times less rapidly than does aluminum. Turbulence is often used in water flows to speed up heat transfer, but turbulence slows down the flow and when pumps are used, increases pumping costs.
Prior art known to the applicant includes the following United States patents:
U.S. Pat. No. 3,725,206--Foley--discloses a desalination plant wherein desalination is provided in a vacuum. A blower moves water vapour from one evacuated area to another. Dense brine and fresh water are removed from these areas by two separate vacuum-liquid pumps.
U.S. Pat. No. 3,390,057--Day--discloses an apparatus for vapour compression distillation of water which utilizes heat transferred from distilled water to vapourize supply water at a reduced pressure.
U.S. Pat. No. 3,494,835--Mahistre--shows a system for desalination of sea water which utilizes a compressor to draw saline water into a tube for vapourization in a vacuum and recycles heat from the condensed vapour to heat the saline water.
U.S. Pat. No. 4,267,022--Pitcher--discloses an apparatus for desalinizing water where heated saline water is evaporated in a low pressure zone created by a vacuum pump.
U.S. Pat. No. 3,930,960--Taylor --teaches a water purification system utilizing a blow down operation to eliminate solid wastes.
U.S. Pat. No. 3,725,205--Heen--discloses an apparatus for cleaning sewage water which employs a reduced pressure evaporation tank and which transfers the vapour to a condensing chamber.
U.S. Pat. No. 4,203,806--Diggs--discloses an apparatus for desalinating water wherein contaminated water is preheated by solar energy before vapourization in a vacuum chamber and the water vapour is condensed in a separate chamber at atmospheric pressure.
U.S. Pat. No. 4,052,267--McFee--shows a water distiller including a blower used to condense the vapourized water.
All of these patents are relatively involved and utilize several moving parts, all of which make such systems unsatisfactory for use in areas hereinbefore described.